diff --git a/src/features/run/rubyTypes.ts b/src/features/run/rubyTypes.ts
index 842845c80..fb22e79b7 100644
--- a/src/features/run/rubyTypes.ts
+++ b/src/features/run/rubyTypes.ts
@@ -10,12 +10,27 @@ import { commandName } from "./commandName";
 
 const on = (v: string | undefined) => v === "true";
 
+const RUBY_TOOLS = new Set(["ruby", "bundle", "rake", "rspec"]);
+
+/**
+ * The launcher for `want` (`bundle` or the tool itself) from the Launcher field. A field holding
+ * the other Ruby tool of the same interpreter (`/v/bin/ruby` when Bundler is ticked) means its
+ * sibling in that directory; anything else (a binstub, `spring`) is the user's own and stays.
+ */
+function launcher(command: string | undefined, want: string): string {
+  const given = command?.trim();
+  if (!given) return want;
+  const current = commandName(given);
+  if (current === want || !RUBY_TOOLS.has(current)) return given;
+  const dir = /^.*[/\\]/.exec(given)?.[0] ?? "";
+  return dir + want + (/\.exe$/i.test(given) ? ".exe" : "");
+}
+
 /** `bundle exec <tool>` or `<tool>`, launched through `params.command` when one is set. */
 function tool(p: Readonly<Record<string, string>>, name: string): { command: string; args: string[] } {
-  const command = p.command?.trim();
   return on(p.bundler)
-    ? { command: command || "bundle", args: ["exec", name] }
-    : { command: command || name, args: [] };
+    ? { command: launcher(p.command, "bundle"), args: ["exec", name] }
+    : { command: launcher(p.command, name), args: [] };
 }
 
 /** Splits `bundle exec <tool> rest…` / `<tool> rest…` into the launcher, the Bundler flag and `rest`. */
diff --git a/src/features/run/runConfigTypes.test.tsx b/src/features/run/runConfigTypes.test.tsx
index e8b412abf..bdff433c7 100644
--- a/src/features/run/runConfigTypes.test.tsx
+++ b/src/features/run/runConfigTypes.test.tsx
@@ -225,6 +225,24 @@ describe("configuration types", () => {
     });
   });
 
+  it("ticking Bundler swaps the interpreter launcher for its bundle sibling, and back", () => {
+    const abs = "/v/ruby/bin/ruby";
+    const run = cfg("r", { kind: "ruby", command: abs, args: ["-Ilib", "test/a_test.rb"] });
+    expect(withParams(run, { ...formParams(run)!, bundler: "true" })).toMatchObject({
+      command: "/v/ruby/bin/bundle",
+      args: ["exec", "ruby", "-Ilib", "test/a_test.rb"],
+    });
+    const bundled = cfg("r", { kind: "ruby", command: "/v/ruby/bin/bundle", args: ["exec", "ruby", "a.rb"] });
+    expect(withParams(bundled, { ...formParams(bundled)!, bundler: "" })).toMatchObject({
+      command: "/v/ruby/bin/ruby",
+      args: ["a.rb"],
+    });
+    // A launcher of the user's own (binstub, spring) is kept.
+    expect(withParams(run, { ...formParams(run)!, bundler: "true", command: "bin/spring" })).toMatchObject({
+      command: "bin/spring",
+    });
+  });
+
   it("ruby types keep option values with their options and the argument order as written", () => {
     const ruby = (args: string[]) => formParams(cfg("r", { kind: "ruby", command: "ruby", args }));
     expect(ruby(["-I", "lib", "-w", "bin/app", "--port", "3000"])).toEqual({